It is known in the art relating to internal combustion engines, such as diesel engines, to actuate two adjacent valves of an engine cylinder by a cam actuated rocker arm acting through a valve bridge. The valve bridge may incorporate two hydraulic lash adjuster assemblies which are received in recesses near opposite ends of the valve bridge to engage and directly act upon the ends of the valve stems. Examples of prior proposed arrangements are shown in U.S. Pat. Nos. 2,380,051 Kettering issued July 10, 1945 and 3,140,698 Voorhies issued July 14, 1964.
In these prior arrangements, the lash adjuster assemblies are retained in pressure oil receiving recesses, either by press fitting or by screw thread retention, both of which are shown by U.S. Pat. No. 2,380,051. The traditional press fit arrangement of U.S. Pat. No. 2,380,051 provides an outer shell 42 (holder) held in a recess 37, 39 and receiving a reciprocable piston 44 (body) that directly engages an associated valve. In U.S. Pat. No. 3,140,698, a plunger 27 is added inside the reciprocable body (which also acts as a cylinder 24) and the holder is in the form of a bushing 21.
In both arrangements, sufficient clearance must be provided between the holder and the reciprocable body to avoid binding of the body due to distortion of the holder from its press fitting into the valve bridge recess. In operation, this distortion and the necessary clearance can result in an excessive loss of pressure oil from the valve bridge between the holder and body. While the oil loss would be reduced in the arrangement of U.S. Pat. No. 3,140,698 by retaining the higher pressures inside the reciprocable body 21, the effect may still be significant. Similar effects could result from distortion of an alternative threaded holder screwed tightly into a valve bridge recess, as has also been previously proposed.